Thanks for the query.
Your symptoms of irregular periods
suggests hormonal imbalance.
I recommend you to get a transvaginal ultrasound
done to rule out polycystic ovary.
You need to take hormones in the form of oral contraceptive pills
for atleast 6 months.
Reduce your weight if you are overweight.
Even 5 % decrease in weight normalizes your menstrual cycle.
Breast tenderness is due to hormone called progesterone
It will subside once your cycles are regular.
Nothing to worry.
Hope this helps.